Sari Horwitz reports in the WaPo:

Florida special prosecutor Angela Corey plans to announce as early as Wednesday afternoon that she is charging neighborhood watch volunteer George Zimmerman in the shooting of Trayvon Martin, according to a law enforcement official close to the investigation.

It was not immediately clear what charge Zimmerman will face.

Update:  Zimmerman has been arrested and charged with second-degree murder, Gary Fineout and Brendan Farrington report for AP.